AUTHOR=Akazue Pearl Ihuoma , Quashie Neils Ben , Vaughan Sue , de Koning Harry P. , Gwira Theresa Manful 
  
TITLE=Phenotypic profiling of Pathogen Box compounds MMV667494 and MMV028694 in bloodstream-form Trypanosoma brucei brucei
  
JOURNAL=Experimental Biology and Medicine
  
VOLUME=Volume 251 - 2026
  
YEAR=2026
  
URL=https://www.ebm-journal.org/journals/experimental-biology-and-medicine/articles/10.3389/ebm.2026.10979
  
DOI=10.3389/ebm.2026.10979
  
ISSN=1535-3699
  
ABSTRACT=Open-access drug discovery platforms have accelerated hit identification and lead prioritization across multiple diseases and enable systematic repurposing of bioactive compounds beyond their original indications. However, there remains a need for new chemotypes for African trypanosomiasis with improved efficacy and resilience to emerging drug resistance. In this study, we evaluated the antitrypanosomal potential and cellular effects of two Pathogen Box compounds, MMV667494 and MMV028694. The compounds were selected through a resazurin-based in vitro phenotypic viability screen that measures metabolic activity as a proxy for parasite viability against bloodstream-form Trypanosoma brucei brucei. To explore cellular phenotypes consistent with potential mechanisms of action, we applied cytological profiling using flow cytometry- and microscopy-based assays, including Annexin V/propidium iodide staining, cell-cycle DNA-content analysis, mitochondrial membrane potential (TMRE), and mitochondrial reactive oxygen species (MitoSOX) measurements. Both MMV667494 and MMV028694 (IC50 = 0.44 ± 0.05 µM and 0.33 ± 0.03 µM, respectively) displayed sub-micromolar antitrypanosomal potency and preferential toxicity toward trypanosomes over mammalian cells (selectivity indices >10). Growth profiling demonstrated dose-dependent inhibition of parasite proliferation, with evidence of trypanocidal activity at higher concentrations and longer exposure times. Treatment resulted in increased populations of phosphatidylserine-exposed and membrane-compromised cells, which is consistent with apoptosis-like phenotypes in trypanosomes. Although both compounds induced mitochondrial membrane depolarization in treated T. b. brucei cells, this effect was observed predominantly in a subpopulation of cells and is therefore unlikely to represent the primary cause of cell death. Increased mitochondrial production of reactive oxygen species and altered cell-cycle progression were also observed, which might indicate disruption of key cellular processes. These findings shows that MMV667494 and MMV028694 are selective antitrypanosomal compounds and their activities are associated with induce apoptosis-like features, cell-cycle disruption, and mitochondrial stress signatures in bloodstream-form T. b. brucei. These findings provide phenotypic insights into the activity of the compounds, warranting further target deconvolution and optimization, although validation in human-infective subspecies and in vivo systems will be required.